(1) Field of the Invention
The present invention pertains to coatings and metal surface treatments preparatory to applying such coatings.
(2) Description of the Prior Art
Many attempts have been made to improve the salt spray protection provided by protective coatings including among others, improvements in compositions of coating materials and also pretreatments prior to coatings to modify the chemical surface for better bond with the protective coating.
U.S. Pat. No. 2,528,535 to Merker teaches phosphating oil-in-water systems for lubricating compositions, preferably with oxidation inhibitors and mentions the possibility of adding and rust corrosion inhibitors, preferably less than 3% by weight.
U.S. Pat. No. 3,457,173 to Pater lubricates metal surfaces by applying siloxane-polyoxyalkylene block co-polymers.
Soviet Union Pat. No. 0810782 teaches polymerized cotton seed oil apparently used as a lubricant.
U.S. Pat. No. 4,440,582 to Smith, et al. claims coating compositions consisting essentially of phosphating oil, polysiloxane or alkypolysiloxane and water and expresses a preference for applying such coating compositions to metal parts which have been phosphated.
None of the above references teach the surprising improvement obtained by the present invention's use of sorbitan and preferably also alkaline earth, e.g. barium, sulfonates.
It is particularly surprising that, in spite of the teaching of U.S. Pat. No. 4,440,582 that the compositions should consist essentially of (be restricted to) phosphating oils, silioxanes and water, the present invention involves the discovery that very substantial increases in performance can be obtained by adding one or more of the additional ingredients disclosed herein.